A very useful comeback to being called an egg. Decided to share it, as it can be quite useful to GNC and possibly even trans people who find themselves in this situation.
Also a good thing of note is that calling people eggs is a violation of the egg prime directive, and is considered invalidating as you are trying to say that a person is not the gender they identify as, that their identity is invalid. Don't call people eggs, like ever, it's extremely uncool.
It means to call someone trans in denial. It's a big thing in communities like r/egg_irl and it can be quite toxic.